Optical character spacing system for phototypesetting

ABSTRACT

A character image projection system successively projects image bearing light beams along a common optical axis toward a photosensitive surface. The images of the individual characters are spaced on the photosensitive surface to form lines of composition. The spacing is accomplished by collimating the image bearing light beams, then diverting the collimated beam by means of a movable reflecting surface into a refocusing and scan lens assembly from which the light beams emit onto the photosensitive surface. The position of the reflector may be controlled by a servo mechanism which responds to character image space information from a computer. The refocusing and scan lens assembly incorporates compensation for the angular position of the reflecting member whereby the character images remain in focus and are properly spaced even though the photosensitive surface is maintained flat at the image plane of the system.

, w 1:, XF? 3965389984 I v muumvu uaMLEIS g I} Rosin June 13, 1972OPTICAL CHARACTER SPACING Artorney-Marechal, Biebel, French & BuggSYSTEM F OR PHOTOTYPESETTING I [72] Inventor: Seymour Rosin, Massapequa,NY. [73] Assignee: HarrisJmenype Corporation, Cleveland, A characterimage PI'OJfiCUOH system successively pro ects 57 ABSTRACT Ohio imagebearing light beams along a common optical axis I toward aphotosensitive surface. The images of the individual [22] Filed: May 4,1970 characters are spaced on the photosensitive surface to form I ppNo: 34,300 lines of composition. The spacing is accomplished bycollimat- 8 ing the image bean'ng light beams, then diverting thecollimated beam by means of a movable reflecting surface into arefocusing and scan lens assembly from which the light beams 52 U.S.Cl..95 4.s 51 Int.C1 5s FieldofSear-ch ..95 4.5

reflector may be controlled by a servo mechanism which responds tocharacter image space information from a computer. The refocusing andscan lens assembly incorporates UNITED STATES PATENTS compensation forthe angular position of the reflecting member whereby the characterimages remain in focus and 3,106,880 10/1963 Rossetto ...95/4.5

are properly spaced even though the photosensitive surface is 3,509,8045/1970 Kohler "9514.5 maintained fl t at the image plans fm System,

[ 56] References Cited Primary E.raminer.lohn M. Horan 6 Claims, 4Drawing Figures FLASH fl y t 42 SELECTOR B CIRCUITS 32 i ea umnog s5CHARACTER ERVO SELECTOR so 6 r ---1 1o 84' MEMORY I TAPE I I CHARWIDTHREADER I JUSTIFY 1 K 65 "B41b21/22 emit onto the photosensitive surface.The position of the OPTICAL CHARACTER SPACING SYSTEM FORPHOTOTYPESETTING CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OFTHE INVENTION This invention relates to high speed phototypesettingmachines of the kind in which characters for the formation of lines ofcomposition are selected from input information, usually in the form ofselection codes, and image bearing light beams of the individualcharacters, in the order of selection, are directed to differentpositions on a photosensitive surface, such as photographic film orpaper. In the past various arrangements have been made for the directingof the image bearing light beams to the correct positions, insuccession, for spacing of the images formed on the photosensitivesurface. These prior art arrangements to a great extent form a majorlimitation upon the total speed capacity of the system. The systemsrequire stopping and starting of members which have appreciable inertia.In one system used in a number of different machines, the light beamsare collimated and then directed into a refocusing lens and a rightangle reflector assembly which are mounted on a movable carriage. Thiscarriage is moved across the photosensitive surface by amountscorresponding to the width of the character images and thus placing thecharacter image in proper position, in succession, to form lines ofcomposition. This achieves variable character spacing according to thecharacter image widths, and with lines justified by interword, and insome cases intercharacter, spacing. Another form of device employs acarriage which moves the entire width of the photosensitive sufface, forexample by directing the loop of film from a supply roll into a movablecarriage, whereby the loop provides sufficient flexibility toaccommodate carriage movement and the carriage movement causesdisplacement of the light beams on the photosensitive surface. In eitherevent, a movable carriage is required which must follow a stop-startsequence to achieve the proper character spacing. Efforts to make thesecarriages light in weight have been partially successful, butnevertheless there is still enough inertia involved, particularly whenit is desired to achieve character images in the sum of 50 charactersper second and higher, while retaining the high quality expected ofphototypesetting apparatus.

Suggestions have been made in the prior art for spacing of characters onthe photosensitive surface through the use of rotatable reflectingmembers, such as a mirror, which is moved to different angular positionsand therefore reflects the image bearing light beams to differentregions of the photosensitive surface in order to achieve characterspacing U.S. Pat. No. 1,175,685, issued Mar. 14, 1916, discloses atypical such system, wherein the photosensitive surface is mounted in aflat image plane, and a movable optical system is incorporated inconjunction with the angularly moving mirror in order to maintain properfocus of the character images. Other suggestions have been made usingangularly movable or rotatable mirrors or reflectors, in which the filmis mounted along an are which has the center of rotation of the mirroras its focus. This has been found, however, to result in some distortionin the character images, since they are being focused onto thephotosensitive surface along a short are, rather than over a flat plane.Furthermore, handling of photosensitive materials, particularly film, issomewhat difficult and when the film in particular is curvedtransversely to its length, it is difficult to maintain it accuratelyacross the desired arc, hence this arrangement has considerablepractical drawbacks.

SUMMARY OF THE INVENTION In accordance with the present invention,successive image bearing light beams of the characters to form lines ofcomposi- 1x A I 3,668,984

tion are produced by equipment which is known per se, and the size ofthe images may be controlled by known meansr The path of the imagebearing light beams is directed through the collimating lens system (insome cases part of the size control) which collimates the image bearingbeam into parallel rays and the collimated beam is directed to arotating reflector such as a mirror. The angular WWW trolled by a servomotor system which holds the mirror in selected different angularpositions with the accuracy necessary for phototypesetting quality. Theservo motor is controlled in accordance with the image width informationderived at the time of selection of thecharacter, by apparatus which isper se known. The collimated beams are 'thus reflected to differentlocations, and a scan and refocusing lens assembly receives these beams,at the different an ular locations, from the rotatable reflector, anddirects the beams onto the photosensi; tive surface. This surface, suchas photographic film or paper, is mounted in an image plane and the scanlens assembly focuses the image bearing beams in this plane, to formsuccessive properly sized images of the individual characters, in theproper succession.

With regard to this point, a desirable arrangement, and probably themost practicable one, dictates that any angular displacement of themirror should have its counterpart in a linear displacement on the filmplane. This should be true whether the angle is relatively large, suchas that needed to change from the center to edge of the line, orrelatively small such as that needed to change from one character to thenext, and this relationship should hold anywhere in the line.

In order to achieve this, the optical system should have propertiesdifferent from those of normal, or so-called distortion free, lenses.For the latter (FIG. 3, hereinafter described) consider collimated lightwhich, falling on lens L from the left will be converged to a point A ata distance from the lens. The relationship from the diagram can then bewritten as:

y f tan 0 where y is the distance of .A from theoptical axis.

Relating this to an actual system, the point A is on the film and thelatter is intersected by the optical axis XX in the center of the line.From equation l it is seen that the relationship between angular motion0 in the collimated space and interval y on the film, is non-linear.Further, upon differentiating l we get dy=fsec 0d6 (2) which gives therelationship for small displacements dy on the film to d6 for angle(character interval).

By changing 1 so that it reads:

3 =f" 6 (1) and its differential then becomes dy f d6 2 and both largeand small displacements become linear and independent of position on theline.

The scan lens assembly thus is of a special construction which obeys therelationship of formula 1' instead of formula I, and compensates fordistortion of the image size at the extreme angular positi mwmlgeithegsidg of a mid position in which beams reflected from it wouldintersect the photosensitive surface at right angles. The scan lensassembly then has designed into it compensation for changes in focus dueto the increase in length of the optical path as the light beamsintersect the photosensitive surface at angles decreasing from at eitherends of the lines being composed. Therefore, the scan lens assemblyoperates as a passive element which provides the necessary compensationfor distortion and/or change in focus due to deviation of the light beamfrom direct right angle intersection with the image plane. The result islines of composition which are in focus across the entire width of thecolumn and character images which are sharp, not distorted, and properlyspaced from each other in accordance with typographical quality.

Proper spacing and undistorted images are the most significant thingsabout the special scanning lens design. A camera lens could serve thepurpose of focusing the image on a flat plane, because the lightentering the lens is collimated. The displacement of the image along thebase line would not be directly proportional to the angle of rotation ofthe mirror, however, but it would be directly proportional to thetangent of the angle. The width of the image itself would also beproportional to the tangent of the angle of rotation.

The spacing distortion might be, with difficulty, compensated byrotating the mirror in step sizes modified by the tangent function. Theangle of rotation for a character ofa given size would be different atthe end of the line than at the center. But, this still would notcompensate for the distortion of the width of the image. The specialscan lens also accomplishes that correction, and the entire dualfunction is achieved in a passive element.

The primary object of the invention, therefore, is to provide a novelphototypesetting machine, and particularly a novel character spacingapparatus for such machine, wherein lightweight low-inertia moving partsare employed with novel passive or nonmoving elements for purposes ofspacing the images of successively projected characters.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showingthe phototypesetting machine and its character spacing apparatus, asprovided by the invention, together with block diagram illustrations ofthe controls therefor;

FIG. 2 is a fragmentary view of the typical character font disc whichmay be employed in the apparatus shown in FIG. 1, illustrating thecharacter selection code and the font selection prisms used inconjunction with the-character selection and projecting system;

FIG. 3 is-a diagram showing relationships in the optical system; and

FIG. 4 is a detail drawing of the scan lens.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thecharacter image projecting system includes a continuously rotatingcharacter font disc 10 which may be of the type shown in U.S. Pat. No.3,223,017, although the character width information may be omitted fromthe disc in this particular instance. As shown in FIG. 2, the discincludes at least two font circles 11 and 12, each of which includes afull font oftype, different from the other, as a transparency through anopaque background. The character selection code, unique for eachcharacter in the font, is contained within a separate zone 14. Furtherdetails regarding the selection code and its use are described in U.S.Pat. No. 3,059,219.

The selection code in zone 14 cooperates with a pair of photocells l andcooperating light sources 16 to generate character selection pulseswhich are directed to selector circuits 18 that in turn control a flashcontrol unit 20. This unit drives a high speed flash lamp 22 (or acorresponding spark gap) which creates an intense beam of light, havinga short time duration in the order of a microsecond. This light passesthrough the font selector prisms 25 which are located on either side ofthe disc 10, and exits from these prisms along an optical path 26 whichis common to the successively connected images. Details of theconstruction and operation of the font prism system are disclosed inU.S. Pat. No. 3,099,945.

The image bearing light beams then proceed through one of a plurality ofsizing lenses 28 carried for example in a turret 29 such that anyselected one of these lenses is movable into the optical path, thuschanging the size ofthe resultant image. A1- ternatively, adjustablecharacter sizing lenses could be employed. In any event, the sizing lenswhich is in the operation position produces a real image of thecharacter at a field lens 30, which is essentially operative to gatherthe light rays for the further operation of the optical system. Theimage bearing beams proceed from the field lens 30 to a reflector systemshown schematically at 32, in which the light is redirected asnecessary. This system may include prisms with multiple reflectingsurfaces for orienting the character images as negessary, however forsimplification there is shown merely a single reflecting surface.

The light beams then pass to a collimating lens system 35. Thiscollimating lens preferably has some adjustment of its focal length,sufficient for initial set-up and precise focusing, but once thisadjustment is made, ordinarily the collimating lens is not furtheradjusted. The collimated light beams emitted from the collimating lens35 are directed onto a rotatable reflector or mirror 40 which isconnected to the shaft 42 of a servo motor 44 which functions as a meansfor selectively changing the angularity of the reflection of thecollimated lens, in order to direct the collimated light beams todifferent portions of a photosensitive surface 45, which may be forexample photographic film or paper from a supply r011 46, passing to atake-up roll 47 under the control of a motor 48 that functions as aleading or line spacing control for the spacing ofsuccessive lines ofcomposition. The reflector 40 directs light to the plane of thephotosensitive material 45 in such a way that the center ofa line to beformed on the material 45 is at a point at right angles to the beam oflight coming from the reflector 40. Thus, the reflector displaces thebeams to either side of this center path.

Between the reflector 40 and the image plane defined by the position ofthe photosensitive material 45, there is a scan or refocusing lens 50which functions to focus the collimated light beams and thus produceareal image at the image plane and on the photosensitive material. Atthe same time, this scan lens provides compensation for the angularityof light beams striking the photosensitive surface at some angle lessthan as when the light beams are displaced to either side of the center.Obviously, the farther the light beams are displaced in eitherdirection, the more acute this angle will become, and in an ordinaryoptical system this would produce blurring of the images due to changein optical path, and would also produce a distortion of the image, withthe character image tending to become wider as it is displaced fartherfrom the center mark.

The scan lens 50 thus functions as a passive element which provides forproper focus and sizing and spacing of the character images, whilepermitting the photosensitive material to be supported in a plane. Thisscan lens is ofa special design, such that light being focused by itobeys the relationship y =f' 9 rather than the more usual y f tan 9, asshown in FIG. 3.

The specifications for a typical scan lens, which has been usedsuccessfully, are as follows:

Surf. Radius C.A./2 Thickness lndex/ Elemm mm t(mm) Dispersion ment a.STOP 11.08 79.84

b. l1l.870 30.84 5.94 1.707.542 1 g. 2677.500 39.77 11.83 1.707.542 IVVarious controls and devices can be used for the selection an spacing ofthe characters to produce justified lines of composition. By way ofexample the selector circuits may be of the type described and shown in1.1.8. Pat. No. 3,339,470 issued Sept. 5, 1967. These circuits arecontrolled through a character selector 55 receiving character codesfrom a master control unit 60, particularly from its memory or registersection 62.

The control unit also includes a character width memory tion systemadapted to create selectively different characters along a commonoptical axis,

means for supporting a photosensitive surface in an image plane spacedfrom said projection system,

an improved optical spacing system comprising a series of opticalelements including a collimating lens receiving light beams from saidprojection system,

selectively movable means for changing angularly the direction of thecollimated beams according to desired 64, into which is loaded all ofthe unique typographic widths 10 character image spacing,

for the various characters on the font 10. A justification coma scanlens receiving the collimated beams from said movaputer section 65 alsois incorporated in the control unit to calble means and refocusing thebeams to produce images culate the widths of interword spaces necessaryto make on the photosensitive surface, said scan lens includingjustified lines of the words and characters making up a line. meansconstructed and arranged to adjust the beams ac- The control unit 60transmits character identification codes cording to the relationship tothe selector 55, and width information to the mirror servo control 68which in turn drives the motor 44. Preferably a positional encoder 69 isalso driven from motor 44, and connected in a feedback loop to the servocontrol 68. The control unit receives input information from anysuitable source, such as a tape reader 70. The reader may be used toload width information into the character width memory, and also to feedcharacter codes and function codes to the memory 62, preferably in theform of a sufficient number of codes to complete a single line ofcomposition and cause sufficient movement of the leading motor 48 to beready to commence the next line.

It should be noted that while a preferred embodiment is shown in FIG. I,certain simplifications of the system are possible. The size control canbe omitted, and different sizes of master characters employed, orvariable character image size not provided at all. The field lens andreflector system 32 can be omitted, with the projection system (flashsource and disc) feeding directly into the collimating lens 35. Alsosuitable choice of size control lenses, and arranging them to act ascollimating lenses feeding directly to the reflector 40, can providefurther simplification ofthe system.

While the form of apparatus herein described constitutes a preferredembodiment of the invention, it is to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

30 field lens.

y =f' 6, where y is the distance of the image from the intersection ofthe axis of the scan lens and the image plane, f is the effective focallength of the scan lens, and 0 is the angle between the collimated beamsand the optical axis of the scan lens.

2. A phototypesetting machine as defined in claim 1, including amagnification lens between said projection system and said collimatinglens, and a field lens receiving light from said magnification lens andgathering the light into said collimatin g lens.

3. A phototypesetting machine as defined in claim 2, including aplurality of magnification lenses and mechanism for selectively movingone of said magnification lenses into operating position between saidprojection system and said rotatable about an axis at right angles tosuch collimated beams.

5. A p'hototypesetting machine as defined in claim 4, wherein saidreflecting member is rotatable about an axis parallel to the verticaldimension of the character field of the 0 character images to cause sideby side spacing of the character images on the photosensitive surface.

6. A phototypesetting machine as defined in claim 5, including a servomotor connected to control the angular position of said reflectingmember.

1. In a phototypesetting machine having a character projec- UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 66 8 9 84Dated June 13 1972 Inventor(s) Seymour Rosin It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below: 7

Amendment A filed in the Patent Office on August 16, 1971 was partiallyentered during the printing of the patent. In Column 4, line 68, thefollowing sentence was not entered by the Patent Office.

-Surface a is merely a mask opening (not shown) to the left of elementI.---

Signed and scaled this 20th day of February 1973.

(SEAL) Attest:

EDWARD MFLETCHERJR. ROBERT GOTTSCHALK Commissioner of Patents AttestingOfficer

1. In a phototypesetting machine having a character projection systemadapted to create selectively different characters along a commonoptical axis, means for supporting a photosensitive surface in an imageplane spaced from said projection system, an improved optical spacingsystem comprising a series of optical elements including a collimatinglens receiving light beams from said projection system, selectivelymovable means for changing angularly the direction of the collimatedbeams according to desired character image spacing, a scan lensreceiving the collimated beams from said movable means and refocusingthe beams to produce images on the photosensitive surface, said scanlens including means constructed and arranged to adjust the beamsaccording to the relationship y'' f . theta , where y'' is the distanceof the image from the intersection of the axis of the scan lens and theimage plane, f is the effective focal length of the scan lens, and thetais the angle between the collimated beams and the optical axis of thescan lens.
 2. A phototypesetting machine as defined in claim 1,including a magnification lens between said projection system and saidcollimating lens, and a field lens receiving light from saidmagnification lens and gathering the light into said collimating lens.3. A phototypesetting machine as defined in claim 2, including aplurality of magnification lenses and mechanism for selectively movingone of said magnification lenses into operating position between saidprojection system and said field lens.
 4. A phototypesetting machine asdefined in claim 1, wherein said movable means for changing the angulardirection of the collimated beams is a reflecting member intersectingthe beams emitting from said collimating lens and rotatable about anaxis at right angles to such collimated beams.
 5. A phototypesettingmachine as defined in claim 4, wherein said reflecting member isrotatable about an axis parallel to the vertical dimension of thecharacter field of the character images to cause side by side spacing ofthe character images on the photosensitive surface.
 6. Aphototypesetting machine as defined in claim 5, including a servo motorconnected to control the angular position of said reflecting member.